WO2004080599 discloses a method for controlling the partial pressure of oxygen when mutually separating minerals in the different process steps of the separation process. In order to control the partial pressure of oxygen, the gases fed in the different process steps are recirculated in an essentially closed gas circulation created around the equipment used in the different process steps, so that the gas recirculation is controlled by measuring the potential of the slurry containing valuable minerals.
WO2015007955 discloses a method for gas handling in a mineral flotation circuit maintained under an essentially closed recirculating gas atmosphere. Pressurized process gas is fed as a flotation gas into one of more sealed flotation cells, which are maintained under an overpressure of 2-10 mbar, preferably 5-8 mbar. Process gas is collected from the tops of the flotation cells and recirculated to a blower, which pressurizes the process gas and feeds it back to the flotation cells. The pressure in the suction side of the blower is balanced with help of a level controlled gas buffer tank. The suction side of the blower this arrangement is slightly overpressurized, which elevates the risk of having leaks to ambient. Also placement of a gas buffer tank in the main recirculation loop requires the tank to be of large volume due to a large amount of gas flow to be balanced rendering it expensive and more difficult to fit into the plant layout as it takes a lot of space.